Cleaning blade for photocopier

ABSTRACT

An apparatus and method for cleaning liquid developer from support surfaces, such as reusable surfaces used for carrying latent electrostatic images, is described. Surfaces are cleaned by a blade having a configuration which deflects material away from the surface undergoing cleaning while it cleans the surface as a scraper blade. The blade provides a scraper function in addition to conveying the liquid developer cleaned from the surface to a retention reservoir.

United States Patent 11 1 Hwa 5] Nov. 11, 1975 1 41 CLEANING BLADE FORPHOTOCOPIER 3.552.850 1/1971 Royka et a1 355/15 5] Inventor: S phen C.P- Hwa, penfield NIY. 3.742.551 7/1973 .Or1e1 355/15 X [73] Assignee:Xerox Corporation, Starnford, FOREIGN PATENTS OR APPLICATIONS Conn 21l1,509 9/1971 Germany 355/15 [22] Filed: May 1974 PrimaryE.\uminer12ichard L. Moses [21] APPL 473 535 Attorney, Agent, orFirm-James J. Ralabate; Donald C. Kolasch; Ernest F. Chapman [30]Foreign Application Priority Data June 29. 1973 United Kingdom .531045/73 [57] ABSTRACT An apparatus and method for cleaning 11qu1ddevel- 52 us CL 355 5; 5 5 ug oper from support surfaces, such asreusable surfaces 7 355/10 used for carrying latent electrostaticimages, is de- [51 Int. Cl. G03G 21/00 scribed Surfaces are Cleaned by ablade having a [58] Field of Search 355/15, 10, 3 R; figuration whichdeflects material away from the |18/D]G 117/37 15/25651, L5 faceundergoing cleaning while it cleans the surface as a scraper blade Theblade provides a scraper function 5 References cu in addition toconveying the liquid developer cleaned UNITED STATES PATENTS from thesurface to a retention reservoir. 3.144.674 8/1964 Broughton 15/2565 6Claims. 2 Drawing Figures US. Patent Nov. 11, 1975 CLEANING BLADE FORPHOTOCOPIER BACKGROUND OF THE INVENTION This invention relatesto'cleaning material from'a support surface, and more particularly, itrelates to an apparatus and method for" liquid developer from aphotoconductive other surface.

In the development of electrostatic latent images where liquiddevelopers are used to develop the image on the reusable photoconductorsurface or on a reusable interposition surface, liquid developer remainson the surface after the developer image is transferred to a substrate.In these processes and apparatuses where the surface is reused todevelop subsequent images, the residualliquid developer must be removedtherefrom to such an extent that the residual developer will notinterfere with subsequent imaging causing image or nonimage patterns andsmudges of developer which transfer to subsequent substrates. Cleaningblades are commonly used to remove the residual liquid developers fromthese and other support surfaces.

U.S. Pat. No. 3,660,863 issued to Gerbasi on May 9, 1972, discloses ascraper blade acting on a xerographic drum for removing particulatetoner material from the drum. In Gerbasi, the cutting edge of the blade,that is, the edge of the blade formed by the upper face surface or topsurface and the front side surface, is positioned slightly below thehorizontal center line of the drum and the cutting edge held in a mannerto readily cut or chisel the particulate toner material from the drumsurface. This configuration works fine for particulate toner material,however, when used with liquid developers this configuration causesfluids to permeate machine parts when they drip from the support surfacein various spots. Blade cleaning is also described by Royka et al in US.Pat. No. 3,552,850 wherein at least oneself-adjusting flexible cleaningblade for pressure contact cleaning of theimaging surface is shown. InRoyka et al, the leading edge of at least one cleaning blade ispreferably positioned to form an acute angle of less than about 90 andgreater than about 20 with the confronting portion of the imagingsurface or plane tangent to the imaging surface at the line of bladecontactto clean particulate toner from photoconductive members whenmeans to supply a dry solid lubricant to the imaging surface areprovided. As discussed above, this cleaning technique is operable forparticulate toner, but when liquid developers are used, the fluidscollect on the photoconductive members and fall into machine parts invarious locations of the copier. Furthermore, the wiping action does notsuitably remove the liquid developers from the surface.

In accordance-with .the present invention cleaning blades may bedesignated as scraper blades or wiper blades. A scraper blade is definedas one wherein the stem extends towards the top in the upstreamdirection of the drums movement and when pressed against the drum exertsa chiselling action on the material on the drum surface. When such ablade is used for cleaning liquid material from a support surfacejwhichin operation moves uphill, problems are encountered in disposing of theliquid cleaned or removed from the surface. It may run back over theuncleaned part of the surface and drip offat random positions.

A blade which in operation is pressed against a support surface so thatit is bent along itslength in the downstream direction of the drummotion has a wiping action as it tends to be lifted up by materialmoving with the drum surface, but will wipe any material moving in theopposite direction away from the drum surface. A wiper blade is definedin accordance with the present invention as one in which the stemextends in the downstream direction of the drum motion. As used herein,upstream and downstream refer to drum motion.

OBJECTS OF THE INVENTION It is an object of this invention to provide anapparatus and method for improving the cleaning of reusable surfacesused in electrostatic copying machines employing liquid developers fordevelopment of the image.

Another object of this invention is to provide an apparatus and methodto improve the removal of liquid developer from reusable surfaces whenscraper blades are used as the cleaning blades.

Another object of this invention is to provide an apparatus and methodto prevent the liquid developer cleaned from a reusable surface in anelectrostatic copying machine, from running back over the uncleaned partof the surface causing it to drip off at random positions.

SUMMARY OF THE INVENTION These and other objects are accomplished byproviding a cleaning apparatus for cleaning material from a supportsurface adapted to move in a given direction, a cleaning blade with atip and first or upper stem portion adapted to be mounted as a scraperblade as herein defined in contact with the support surface, and with alower stem portion extending towards the tip portion with a component insaid given direction.

When such a blade is used in conjunction with another scraper bladedownstream in said given direction, the lower stem portion acts todeflect material (liquid developer) moving in opposition to said givendirection away from the surface, while the tip and upper stem portionacts as a separate scraper blade.

According to the present invention, there is provided a method ofsimultaneously removing and deflecting liquid developer from a movingsupport surface, for example, a photoconductive surface in anelectrostatic copying machine, by providing a scraper blade in contactwith the support surface and having a lower stem portion extendingtowards the tip portion with a component in said given direction. Inessence, the method of deflecting liquid developer from a surfacecapable of moving in a given direction and capable of carrying anelectrostatic latent image comprises engaging at least one scraper bladewith the surface capable of carrying an electrostatic latent image, saidscraper blade having an upper stem portion extending opposite said givendirection to a point of contact of the upper stem portion with saidsurface, said point of contact on the upper stern portion being acutting tip, and a lower stem portion extending towards the upper stemportion in said given direction until it intersects and forms an anglewith the upper stem portion, the upper stern portion having a drip tipadjacent the point of contact of the upper stern portion with saidsurface and moving the surface capable of carrying an electrostaticlatent image in a given direction, whereby the cutting tip removesliquid developer from said surface and deflects the removed liquiddeveloper from said surface at the drip tip.

'Additional objects of this invention will become apparent to thoseversed in the art of electrostatic copying machines in view of thefollowing detailed description of the method and apparatus taken inconjunction with the accompanying drawings in which preferredembodiments of the apparatus are shown.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a sectional view of ascraper blade of the present invention.

FIG. 2 shows a schematic sectional view of an electrostatographiccopying apparatus wherein the cleaning station comprises two scraperblades of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The cleaning station mode shownin FIG. 1 illustrates the novel scraper blade of the present inventionand the manner in which the blade operates. The blade is L- shaped andmay be described as having a tip portion or upper stem portion 33 whichis the base of the L. The upper stem or tip portion 33 is adapted tocontact the support surface of drum 11 at tip 32 as a scraper blade asdefined supra, said drum being adapted to move in a given direction. Theupper stem or tip portion 33 of blade 31 extends towards drum l1 and hasa component culminating in tip 32 directed upstream (counter to thedirection of the drum movement). The blade acts as a scraper, the tip 32of the blade preferably being a 90 angle orany other suitable angle soas to form a cutting or chiselling edge at tip 32.

The tip portion or upper stern portion 33 of blade 31 is preferably ofrectangular longitudinal cross-section and also comprises a drip tip 35which is adjacent cutting tip 32 extending outward from the point atwhich the cutting tip contacts the support surface and preferably in anupstream direction. In the most preferred embodiment cutting tip 32 anddrip tip 35 are tips or points formed from right angle intersections ofthe blade material. Drip tip or point 35 must be located in such amanner that liquid developer on the drum surface and scraped from saidsurface by cutting tip 32 will be conveyed to drip tip 35 where it willbe deflected away from the surface of drum 11.

Cleaning blade 31 as illustrated in FIG. 1 also comprises a lower stemportion 36 connected to the upper stem portion 33 preferably at a 90angle therewith. The lower stem portion 36 is the upstanding portion ofthe L (beyond the angle of the L) and extends towards drum 11, thiscomponent being directed downstream (in the direction of the drummotion). The upper stem portion and lower stem portion of blade 31 arepreferably the same material. Scraper blade 31 is mounted on mountingblock 34 and supports blade 31 by engaging lower stem 36. Mounting block34 may be movably mounted to permit withdrawal of cleaning blade 31 fromthe surface of drum 11 when the apparatus'is out of operation. Bladeportion 36 (lower stem portion) may be detachably mounted to mountingblock 34 to permit replacement of the blade.

As illustrated in FIG. 1, as drum 11 moves in the direction of the arrowin an uphill direction, scraper blade 31 engaging the surface of drum 11at cutting tip 32, scrapes the residual liquid developer 37 (includingsolids such as lint and dust entrained therein) from the surface of drum1] upstream from the cutting tip, the liquid developer accumulates onthe blade edge and developer is showndripping from tip 35 in the form ofdrops (numeral 38:) and'falling in the direction of dotted line 39 tosump or reservoir 25. This novel method of deflecting the liquiddeveloper from the surface of a photoconductive drum "prevents theliquid developer scraped from the photoconductive surface, fromaccumulating in quantities at the scraping edge or tip of the blade andrunning upstream where it tends to drip from the surface at variouslocations into machine parts or into an extensive reservoir system,while at the same time efficient cleaning is accomplished by thescraping action of the blade on the surface of drum 11 to provide asurface downstream from the scraper blade 31 suitably cleaned of liquiddeveloper.

In the copying apparatus illustrated in FIG. 2, a copying drum 11 havinga photoconductive surface is rotated in the direction of the arrow aboutits axis so that the surface passes through a number of processingstations. The copying cycle starts at the charging station A wherein acorona discharge device 12 is energized to a high potential to applycharge to the drum surface. The drum then passes to the exposure stationB where an image is projected on the charged drum surface by an opticalsystem (not shown) to produce an electrostatic latent image. The imageflows so that it moves in synchronism with the moving drum' surface. Thelatent image passes to the development station C at which liquiddeveloper is applied from a reservoir 15 by means of rolls l3 and 14.The roll 13 is a supply roll whose lower portion dips into the liquid inthe reservoir 15 and whose upper portion is spaced by (for example) 0.25mm from the upper roll 14 which has its surface shaped with a helicalgroove. The roll 14 is provided with a flexible doctor blade 16 whichremoves liquid from roll 14 to below the groove upper edges due to thedeformation of the blade into the groove. The developer is attracted byelectrostatic attraction from the remote part of the groove to thelatent image across the gap between them to develop the image. Anexample of this method of development is described in detail in US. Pat.No. 3,084,043 issued to Robert W. Gundlach, which is incorporated hereinby reference, wherein there is claimed a method of development inxerography comprising positioning close but spaced from an electrostaticlatent image on an image bearing surface a substantially continuous filmof electrically conductive ink comprising a homogeneous liquid solution,providing flow aiding elements in physical contact between said ink andsaid image bearing surface, and ap= plying a bias to said ink wherebyink moves along said flow aiding elements and develops saidelectrostatic latent image.

A sheet of paper is fed to a transfer station D by sheet feed apparatus(not shown) to move in synchronism with the drum and is pressed againstthe drum surface by a transfer roll 17 so that the developed image istransferred to the paper which is then conveyed away from the transferstation through a chute (not shown). Any material remaining on the drumafter the transfer station must now be cleaned off at the cleaningstation E After cleaning, electroluminescent strip 18 floods the'drumsurface with lightto discharge any remaining charges, so that the drumcan pass onto the charging station for the beginning of the next cycle.A drive mechanism to move the support surface past the various stationsin succession and to move various other rolls is not' shown. Means tomove these various surfaces can be readily provided by one skilled inthe art.

At the cleaning station in FIG. 2, there are provided two scraper blades21 and 22 as described above and in FIG. 1. The scraper blades aremounted on supporting blocks 23 and 24 respectively, which can be movedaway from drum 11 to withdraw the blades from the drum when they are notin use. If the blades are left pressing hard against a stationary drum,the photoconductive surface may be deformed and the blades may acquire apermanent set. A sump 25 is located below the scraper blades to catchthe liquid from the blades.

Each scraper blade is preferably of polyurethane of 6S Shore A hardness,however, scraper blades having a hardness of about 90 Shore A or higherare also within the scope of the invention. The upper stem portion ofthe scraper blades are preferably about three-fourths inch long and 80thousandths of an inch thick. The blades are clamped on supportingblocks 23 and 24 over about the first third of its length by anysuitable means. The cutting tip of the upper stem portion of the bladesare preferably at a 90 angle with the length of the upper stem portionof the blade so as to form a cutting edge from surfaces at 90. A muchsmaller angle (such as 60) at the cutting edge lends to failure by theedge becoming tucked under the upper stem portion of the blade byfriction. The lower stem portion of the blade preferably extends atabout 25 i to the tangent to the drum at the point of contact (a widervariation of angle being possible to suit different combinations ofblades, liquids and drum surfaces), the blade preferably being slightlyflexed against the drum in operation by the supporting blocks 23 and 24with a force preferably of the order of 10 grams per centimeter. Inaccordance with the present invention, it is preferred that the upperstem portion have a rectangular longitudinal cross-section.

The developer liquid remaining on the drum after the transfer station D,together with any foreign matter, such as paper fibers, reaches scraperblade 21 first. In the mode shown in FIG. 2, the scraper blades 21 and22 then scrape the material from drum 11 forming a bead at the endsurface of each blade as shown in detail in FIG. 1. When this beadreaches a certain size, it will fall into the sump 25 from the drip tipof the first scraper blade or it will fall from the drip tip of thesecond (downstream) scraper blade to the back of the first v scraperblade which then deflects the flowing material into the sump 25. Anyliquid developer falling from the drip tip of the second or subsequentscraper blade 22, falls behind the upper stem portion or upon the lowerstem portion of blade 21 and is eventually guided to sump 25 by thelower stem portion of blade 21. The same deflection of liquid developeroccurs in those embodiments (not shown) wherein the second or downstreamscraper blade 22 is a conventional non-angular or flexed scraper bladehaving no drip tip in which case the liquid developer collected therebyruns down the surface of drum 11 and collects behind the upper stemportion of blade 21 until it overflows and passes down the lower stemportion of blade 21 where it is directed to sump 25.

At least two scraper blades are preferred because the material reachingthe first scraper blade contains paper fibers which are considered themain cause of blade failure. As paper fibers accumulate at the blade,the

blade ceases to remove all the material from the drum surface. Theprovision of two scraper blades, as in FIG. 2, reduces the failure rateof the cleaning station, since the second scraper blade is likely toremove what the first scraper blade may miss. The paper fibers have beenfound to be retained by the first scraper blade, even if they may causethat blade to let some liquid past at the points where the fibers areengaged, so that few paper fibers reach the second blade to cause thatblade to fail.

In accordance with the present invention as set forth in FIG. 1 wherethe cleaning blade is L-shaped, having a tip portion adapted to bemounted as a scraper blade in contact with the photoconductive (support)surface, and a stem portion extending towards the tip portion, a singlescraper blade 31 may be used or multiple scraper blades 31 may be used.Alternatively, as explained supra, one or more scraper blades 31 may beused in conjunction with one or more conventional scraper blades.

In accordance with the stated objects, the present invention provides asuitable apparatus and method for cleaning liquid developer from asurface capable of carrying electrostatic latent images. While thisinvention has been described with reference to the structures and methodsteps disclosed herein, it is not confined to the details set forth; andthis application is intended to cover such modifications or changes asmay come within the purposes of the improvements or the scope of thefollowing claims.

What is claimed is:

1. In an electrostatographic reproducing apparatus comprising a movablesupport surface having a portion moving in operation in a givendirection, means for forming a latent electrostatic image on saidsurface, means for developing the latent image with liquid developer,means for transferring the developer image onto a sheet of transfermaterial and a drive mechanism to move the support surface past saidmeans in succession, the improvement comprising a cleaning apparatus forremoving liquid developer from the support surface comprising a scraperblade with an upper stem portion adapted to be mounted as a scraperblade in contact with the support surface, said upper stern portionhaving a drip tip for deflecting said liquid developer away from saidsurface, said drip tip being located adjacent said point of contact ofthe upper stem portion with said surface, said upper stem portionextending substantially opposite said given direction to the point ofcontact of the upper stem portion with the support surface, and a lowerstem portion extending towards the upper stem portion in a directiontoward the support surface until it intersects and forms an angle withthe upper stem portion, the lower stem portion being mounted to asupport block at the end opposite said intersection.

2. The apparatus of claim 1 wherein the upper stem portion having a driptip is of rectangular longitudinal cross-section.

3. The apparatus of claim 1 further comprising means to remove saidblade having a drip tip from engagement with the support surface.

4. The electrostatographic apparatus of claim 1 wherein the cleaningapparatus comprises at least two of said scraping blades having driptips thereon.

5. The electrostatographic apparatus of claim 1 wherein the drip tipextends outward and in an upstream direction from the point at which theupper stem portion of the blade contacts the support surface.

6. The electrostatographic apparatus of claim 1 wherein the upper sternportion in contact with the support surface and the drip tip compriseright angle intersections of material from which the scraper blade isconstructed.

1. In an electrostatographic reproducing apparatus comprising a movablesupport surface having a portion moving in operation in a givendirecTion, means for forming a latent electrostatic image on saidsurface, means for developing the latent image with liquid developer,means for transferring the developer image onto a sheet of transfermaterial and a drive mechanism to move the support surface past saidmeans in succession, the improvement comprising a cleaning apparatus forremoving liquid developer from the support surface comprising a scraperblade with an upper stem portion adapted to be mounted as a scraperblade in contact with the support surface, said upper stem portionhaving a drip tip for deflecting said liquid developer away from saidsurface, said drip tip being located adjacent said point of contact ofthe upper stem portion with said surface, said upper stem portionextending substantially opposite said given direction to the point ofcontact of the upper stem portion with the support surface, and a lowerstem portion extending towards the upper stem portion in a directiontoward the support surface until it intersects and forms an angle withthe upper stem portion, the lower stem portion being mounted to asupport block at the end opposite said intersection.
 2. The apparatus ofclaim 1 wherein the upper stem portion having a drip tip is ofrectangular longitudinal cross-section.
 3. The apparatus of claim 1further comprising means to remove said blade having a drip tip fromengagement with the support surface.
 4. The electrostatographicapparatus of claim 1 wherein the cleaning apparatus comprises at leasttwo of said scraping blades having drip tips thereon.
 5. Theelectrostatographic apparatus of claim 1 wherein the drip tip extendsoutward and in an upstream direction from the point at which the upperstem portion of the blade contacts the support surface.
 6. Theelectrostatographic apparatus of claim 1 wherein the upper stem portionin contact with the support surface and the drip tip comprise rightangle intersections of material from which the scraper blade isconstructed.